<?php
/**
 * 
 * +------------------------------------------------------------+
 * @category FileCache 
 * +------------------------------------------------------------+
 * Key-Value型文件存储
 * +------------------------------------------------------------+
 *
 * @author anzai <236049524@qq.com>
 * @copyright http://www.judianyun.com 2014
 * @version 1.0
 *
 * Modified at : 2014-6-11 10:18:49
 * 
 * 用法：
 * $cache = new FileCache();
 * $cache->add('key' , 'value');
 * $data = $cache->get('key');
 *
 */
class FileCache{
     private $_file_header_size = 14;
     private $_file_index_name;
     private $_file_data_name;
     private $_file_index;				//索引文件句柄
     private $_file_data;				//数据文件句柄
     private $_node_struct;				//索引结点结构体
     private $_inx_node_size = 36;		//索引结点大小

     public function __construct($file_index="filecache_index.dat", $file_data="filecache_data.dat"){
          $this->_node_struct = array(
               'next'=>array(1, 'V'),
               'prev'=>array(1, 'V'),
              'data_offset'=>array(1,'V'),//数据存储起始位置
              'data_size'=>array(1,'V'),//数据长度
              'ref_count'=>array(1,'V'),//引用此处，模仿PHP的引用计数销毁模式
              'key'=>array(16,'H*'),//存储KEY
          );

          $this->_file_index_name = $file_index;
          $this->_file_data_name = $file_data;

          if(!file_exists($this->_file_index_name)){
               $this->_create_index();
          }else{
               $this->_file_index = fopen($this->_file_index_name, "rb+");
          }

          if(!file_exists($this->_file_data_name)){
               $this->_create_data();
          }else{
               $this->_file_data = fopen($this->_file_data_name, "rb+");//二进制存储需要使用b
          }
     }

     //创建索引文件
     private function _create_index(){
          $this->_file_index = fopen($this->_file_index_name, "wb+");//二进制存储需要使用b
          if(!$this->_file_index) 
               throw new E("Could't open index file:".$this->_file_index_name);

          $this->_index_puts(0, '<'.'?php exit()?'.'>');//定位文件流至起始位置0, 放置php标记防止下载
          $this->_index_puts($this->_file_header_size, pack("V1", 0));
     }


     //创建存储文件
     private function _create_data(){
          $this->_file_data = fopen($this->_file_data_name, "wb+");//二进制存储需要使用b
          if(!$this->_file_index) 
               throw new E("Could't open index file:".$this->_file_data_name);

          $this->_data_puts(0, '<'.'?php exit()?'.'>');//定位文件流至起始位置0, 放置php标记防止下载
     }

     private function _index_puts($offset, $data, $length=false){
          fseek($this->_file_index, $offset);

          if($length)
          fputs($this->_file_index, $data, $length);
          else
          fputs($this->_file_index, $data);
     }

     private function _data_puts($offset, $data, $length=false){
          fseek($this->_file_data, $offset);
          if($length)
          fputs($this->_file_data, $data, $length);
          else
          fputs($this->_file_data, $data);
     }

     /**
     * 文件锁
     * @param $is_block 是否独占、阻塞锁
     */
     private function _lock($file_res, $is_block=true){
          flock($file_res, $is_block ? LOCK_EX : LOCK_EX|LOCK_NB);
     }

     private function _unlock($file_res){
          flock($file_res, LOCK_UN);
     }

     public function add($key, $value){
          $key = md5($key);
          $value = serialize($value);
          $this->_lock($this->_file_index, true);
          $this->_lock($this->_file_data, true);
			
          fseek($this->_file_index, $this->_file_header_size);

          list(, $index_count) = unpack('V1', fread($this->_file_index, 4));

          $data_size = filesize($this->_file_data_name);

          fseek($this->_file_data, $data_size);

          $value_size = strlen($value);

          $this->_data_puts(filesize($this->_file_data_name), $value);

          $node_data = 
          pack("V1V1V1V1V1H32", ($index_count==0) ? 0 : $index_count*$this->_inx_node_size, 0, filesize($this->_file_data_name), strlen($value), 0, $key);

          $index_count++;

          $this->_index_puts($this->_file_header_size, $index_count, 4);

          $this->_index_puts($this->get_new_node_pos($index_count), $node_data);

          $this->_unlock($this->_file_data);
          $this->_unlock($this->_file_index);
     }

     public function get_new_node_pos($index_count){
          return $this->_file_header_size + 4 + $this->_inx_node_size * ($index_count-1);
     }

     public function get_node($key){
          $key = md5($key);
          fseek($this->_file_index, $this->_file_header_size);
          $index_count = fread($this->_file_index, 4);

          if($index_count>0) {
               for ($i=0; $i < $index_count ; $i++) { 
                    fseek($this->_file_index, $this->_file_header_size + 4 + $this->_inx_node_size * $i);
                    $data = fread($this->_file_index, $this->_inx_node_size);
                    $node = unpack("V1next/V1prev/V1data_offset/V1data_size/V1ref_count/H32key", $data);

                    if($key == $node['key']){
                         return $node;
                    }
               }
          }else{
               return null;
          }
     }
     
     public function get($key){
     	$data = $this->get_node($key);
     	if ($data) {
     		return $this->get_data($data['data_offset'], $data['data_size']);
     	}else{
     		return ;
     	}
     }

     public function get_data($offset, $length){
          fseek($this->_file_data, $offset);
          return unserialize(fread($this->_file_data, $length));
     }
}